Telescopes: The Windows to Solar Space

Telescopes are observational instruments that give humanity a look at the
universe beyond Earth. Since their first use in 1609 by Galileo Galilei, they
have contributed greatly to the fields of astronomy and physics. In addition,
they have shattered many superstitions and myths about Earth's place among the
stars, such as the geocentric theory of the Earth being the center of the
universe. Telescopes have undergone many stages of evolution, from simple
two-mirror devices that scanned mountains on the moon, to giant mountain-based
observatories and others that now orbit the Earth to study dark energy and hunt
for alien planets. Telescopes, ultimately, have brought the potential for great
astronomical discovery to the masses, from scientists to amateurs alike.

The History of the Telescope

The first crude telescope, a refractor type, was created by Hans Lippershey, a
German-born maker of lenses, who also patented the design in 1608. Italian
physicist and astronomer Galileo Galilei then built an improved version in 1609,
which he called a "perspicillum." Two years later, the name "telescope" was
given to the device by a math expert named Giovanni Demisiani, which became the
word these instruments were known by. German astronomer Johannes Kepler designed
a telescope with a pair of convex lenses in the same year, which became known as
the "Keplerian telescope." In 1663, James Gregory, a mathematician from
Scotland, designed a reflecting telescope that used mirrors to direct the
telescope's image into an eyepiece. It wasn't until 1674 that Robert Hooke was
able to take Gregor's design and actually build such a telescope, however the
first actual reflector telescope was made by English mathematician Isaac Newton
in 1668. Laurent Cassegrain, a French priest, designed a reflecting telescope in
1672 that used a paraboloid mirror with a secondary hyperboloid mirror. This
"Cassegrain" design marked the birth of modern telescopes, as the design
remained in use even in the 21st century.

In 1729, a lawyer named Chester Moore built a lens that helped to alleviate the
type of image distortion known as a chromatic aberration. This was a major
breakthrough in improving the quality of telescope observations. In 1789, a
German-born composer and astronomer William and Caroline Herschel built the
first giant telescope, the Great Forty-Foot Telescope, in England. Another giant
telescope, the "Leviathan of Parsonstown," was built in 1845 Ireland by William
Parsons. This telescope was the largest reflector-type telescope, in terms of
aperture size, until the Hooker Telescope was completed on Mount Wilson in Los
Angeles in 1917. The largest refractor type telescope ever made, in terms of
lens diameter, was the Great Paris Exhibition Telescope, built in 1900, and
displayed at the Paris 1900 Exposition. The Yerkes telescope in Wisconsin, the
second largest ever made, is the largest refractor telescope currently in
operation.

Telescopes continued to evolve, but until the 20th century they were all some
form of optical telescope, primarily reflector types. In 1931, Karl Jansky, an
American-born radio engineer, provided the idea for a radio telescope, which
engineer Grote Reber built in 1937. The world's largest radio telescope is
currently the Arecibo Observatory in Puerto Rico, with a 1,000 foot dish. During
the 20th century, infrared telescopes also evolved, and due to necessity, some
were launched into space, starting with the Infrared Astronomical Satellite
(IRAS), which was deployed in space in 1983. In 1990, the Hubble Space
Telescope, an optical, infrared and ultraviolet telescope, was launched into
space, and is one of the most advanced space-based telescopes currently in
operation. Other contemporary advanced telescopes include the Spitzer Space
Telescope, the Compton Gamma Ray Observatory, and the Chandra X-ray Observatory.

Telescopes come in a variety of design types. The oldest type of telescope is
the optical telescope, which is broken up into refractors and reflectors.
Refractor telescopes direct light through a series of lenses directly to an
eyepiece at the back end, through which an observer can look. Reflector
telescopes use mirrors to redirect and focus light. Reflector telescopes
overcame refractors in popularity because they produced less serious optical
distortions, and this made them much more valuable to astronomers.

In addition to optical telescopes, there are also infrared telescopes, which
view the universe by observing infrared energy that is not visible to the naked
eye. Infrared telescopes depend on high altitude deployments to reduce
absorption of infrared energy by the atmosphere. They produce the best results,
however, when launched into space. Radio telescopes, built like giant satellite
dishes, scan for radio signals from celestial bodies, which are not absorbed by
the atmosphere. They tend to be very large, with dishes up to 1,000 feet in
diameter, such as the Aricebo Observatory. X-ray telescopes and ultraviolet
telescopes both require high altitudes or deployment in space, and they scan for
x-ray radiation and ultraviolet radiation, respectively. X-ray telescopes are
good at scanning for black holes and neutron stars, while ultraviolet telescopes
provide clues about the evolution of young and old stars, as well as galaxies.
Infrared telescopes are used to find celestial bodies such as stars and planets,
while optical telescopes observe visible light thrown off by heavenly bodies and
galaxies, etcetera. Radio telescopes observe radio wave energy coming from
quasars and neutron stars, and are also instrumental in the search for alien
life, such as the Search for Extraterrestrial Intelligence project, or SETI.

One of the most celebrated telescopes in history is the Hubble Space Telescope
(HST), which was launched into space in 1990. Built with funding from taxpayer
dollars and the European Space Agency and NASA, the HST, named after famous
astronomer Edwin Hubble, is the only space telescope that was designed for
service by astronauts in space. This serviceability proved to be critically
useful when it was discovered that its main mirror was defective, requiring
service. Another four servicing missions were carried out to replace, repair and
upgrade parts in the HST. The HST originally was built with reel-based tape
recording instruments, and was upgraded with solid state storage systems. Two
times a day the HST transmits its data, a total of 120 gigabytes every week, to
a satellite which beams it down to Earth. The data then works its way through
White Sands, New Mexico to its final destination at the Goddard Space Flight
Center in Greenbelt, Maryland.

Usage of the telescope is technically open to anyone, regardless of their
nationality, who can submit a proposal. Amateur astronomers were also invited to
participate, but due to budget cuts, only one project was ever approved. Due to
intense competition for access to the HST, however, only 20 percent of requests
gain approval from the Space Telescope Science Institute. The HST has carried
out many projects, including scanning for merging galaxies, measuring the
expansion of the universe, and searching for planets outside the solar system.
It has also produced a large number of impressive, high quality photographs that
have become famous in their own right. The Hubble Telescope is due to reach the
end of its life in 2020, at which time it may fall out of orbit or be hauled
back to Earth. To facilitate the latter, NASA installed the Soft Capture and
Rendezvous System, which is intended to enable a vessel to come and retrieve the
HST for recovery or safe disposal.

Telescopes, from the time of Galileo, have completely transformed the entire
nature of astronomy. Many superstitious beliefs, such as the Earth being the
center of the universe, were disproven by telescopes. Telescopes have found
asteroids, planets and moons, planetary rings, and even planets outside the
solar system. Galileo used a telescope to measure the height of mountains on the
moon as well as discover sunspots. Telescopes revealed the nature of the Milky
Way Galaxy, such as when Galileo discovered that the "cloud" among the stars was
the galaxy itself, and the cloud was actually made of millions of stars. Using a
telescope, an astronomer named Ole Romer discerned the concept of the speed of
light. Newton's use and improvements of telescopes enabled him to make many
achievements, including his theories concerning gravity. Edwin Hubble used
telescopes to discover that the universe was expanding, and the Hubble Space
Telescope, named in his honor, measured the speed of this expansion. Telescopes
have also spotted and measured the distances of nebulas, black holes, neutron
stars and pulsars, and even giant black holes known as quasars. They are now
helping humanity determine the age of the universe, as well as how it formed and
evolved, and they are a critical tool in humanity's search for alien life and
potentially habitable worlds outside the star system.

The Hubble telescope discerned the approximate age of the universe to be between
13 and 14 billion years old, caught views of young galaxies from near the
beginning of the universe, confirmed the existence of enormous black holes at
the center of many galaxies, measured the actual masses and chemical makeup of
extrasolar planets, and gave humanity a crystal clear view of the Shoemaker-Levy
9 comet when it hit Jupiter. The Keck Observatory, built on the Mauna Kea
volcano in Hawaii in 1990, showed that Mars was emitting methane, and it found
the first concrete signs of an extrasolar planet. Its studies of the giant
asteroid Eris helped demote Pluto from the status of a planet. The Spitzer
Observatory, an infrared telescope, was launched into space in 2003, and was the
first to observe light coming from planets outside the solar system. Spitzer
also captured what is thought to be the infrared energy signatures of stars from
when the universe was just 100 million years old. In 2009 Spitzer, discovered
evidence that two extrasolar planets had collided a few thousand years in the
past. The Kepler space telescope, deployed in 2009, discovered smaller
extrasolar planets, such as one the size of the moon in orbit around the star
known as Kepler-37. At the time it was the smallest extrasolar planet ever
observed.

Even after the Hubble was launched, newer and more powerful telescopes were on
the drawing board for construction and deployment. For instance, the Transiting
Exoplanet Survey (TESS) is a telescope that is scheduled for launch into space
in 2017 to hunt for planets outside the solar system. The James Webb Space
Telescope is set to launch into a position a million miles above Earth, to study
galaxy formation in the earliest years of the universe. The Giant Magellan
Telescope is set to become operational in 2020. Based in Chile, it is intended
to hunt for extrasolar planets and other very distant celestial bodies. Two
years later, in Chile, the Large Synoptic Survey Telescope is planned to come
into service, scanning for potentially dangerous asteroids that could impact
Earth, as well as building a better map of the Milky Way galaxy. NASA has plans
for an Advanced Technology Large-Aperture Space Telescope (ATLAST) to launch
into space in 2030. This telescope's mission will be to scan extrasolar worlds
for life, as well as other potential signs of life such as water, methane, and
ozone.

In 2020, the ground-based Giant Magellan Telescope is slated to become
operational in Chile, and is intended to hunt for extrasolar planets and black
holes, and contribute to the study of dark energy. Another telescope planned for
construction in Chile, the European Extremely Large Telescope, began
construction in 2014 and is being designed to provide direct images of planets
outside the solar system, make observations that will answer questions about
planet formation, more accurately measure the expansion of the universe, and
help scientists with the study of black holes. The Thirty Meter Telescope is an
observatory under construction on Mauna Kea in Hawaii, and will engage in a
variety of projects, such as studying dark matter, the evolution of galaxies,
and searching for signs of life on worlds outside the solar system. The
Wide-Field Infrared Survey Telescope (WFIRST) is planned for construction
starting in 2017 and for launch into space in 2024. Its mission will be to study
dark energy and the expansion of the universe, as well as look for extrasolar
planets. The ARKYD Series 100 telescope is a relatively cheap, 33 pound space
telescope that is planned for use by private citizens to scan for asteroids
within the solar system.